In bearing applications having high speed shafting, such as in turbochargers, auxiliary power units, or small gas turbine engines, a floating bushing is provided between the shaft and bearing housing. Lubricating fluid delivered under pressure to the floating bushing and shaft creates a hydrodynamic film at the bushing/shaft and bushing/housing interfaces to provide the damping necessary for controlling shaft motion.
Because of the small radial clearances present between the bushing and shaft, viscous drag imparts angular momentum to the floating bushing and tends to rotate the floating bushing with the shafting. While some degree of rotation is desirable for the floating bushing in order to optimize wear at the shaft/bushing and bushing/housing interfaces, in high speed shaft applications the rotational velocity of the floating bushing tends to approach that of the shafting due to the viscous drag effects. High floating bushing velocities result in loss of damping and control of the shaft motion and, ultimately, increase the wear at the bushing/shaft interface.
What is needed is a free floating bushing arrangement for use with high speed shafting in which the rotational speed of the bushing is reduced from that of the shafting. Such a bushing arrangement should be particularly adapted for use with turbochargers and, preferably, should reduce the rotational speed of the bushing while maintaining damping and control of the shaft motion and without increasing wear at the bushing/shaft or bushing/housing interfaces.